RM7000-250T View Datasheet(PDF) - PMC-Sierra

Part Name

Description

Manufacturer

RM7000-250T

RM7000™ Microprocessor with On-Chip Secondary Cache Datasheet Released

PMC-Sierra 

RM7000™ Microprocessor with On-Chip Secondary Cache Datasheet

Released

Figure 8 Typical Embedded System Block Diagram

DRAM

Flash/

Boot

ROM

Address

Control

72

8

Latch

RM7000

72 SysAD Bus

SysCmd 72

25

72

Memory I/O

Controller

Tertiary Cache

TcLine, etc. (optional)

x

x

PCI Bus

4.26 System Address/Data Bus

The 64-bit System Address Data (SysAD) bus is used to transfer addresses and data between the

RM7000 and the rest of the system. It is protected with an 8-bit parity check bus, SysADC.

The system interface is configurable to allow easy interfacing to memory and I/O systems of

varying frequencies. The data rate and the bus frequency at which the RM7000 transmits data to

the system interface are programmable via boot time mode control bits. Also, the rate at which the

processor receives data is fully controlled by the external device. Therefore, either a low cost

interface requiring no read or write buffering or a faster, high-performance interface can be

designed to communicate with the RM7000. Again, the system designer has the flexibility to make

these price/performance trade-offs.

4.27 System Command Bus

The RM7000 interface has a 9-bit System Command (SysCmd) bus. The command bus indicates

whether the SysAD bus carries an address or data. If the SysAD bus carries an address, then the

SysCmd bus also indicates what type of transaction is to take place (for example, a read or write).

If the SysAD bus carries data, then the SysCmd bus also gives information about the data (for

example, this is the last data word transmitted, or the data contains an error). The SysCmd bus is

bidirectional to support both processor requests and external requests to the RM7000. Processor

requests are initiated by the RM7000 and responded to by an external device. External requests are

issued by an external device and require the RM7000 to respond.

The RM7000 supports one to eight byte and 32-byte block transfers on the SysAD bus. In the case

of a sub-doubleword transfer, the 3 low-order address bits give the byte address of the transfer, and

the SysCmd bus indicates the number of bytes being transferred.

4.28 Handshake Signals

There are ten handshake signals on the system interface. Two of these, RdRdy* and WrRdy*, are

used by an external device to indicate to the RM7000 whether it can accept a new read or write

Proprietary and Confidential to PMC-Sierra, Inc and for its Customer’s Internal Use

28

Document ID: PMC-2002175, Issue 1

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